simplify a bit

Author: piscisaureus

src/db.rs

@@ -8,7 +8,6 @@ use crate::graph::FileId;
 use crate::graph::Graph;
 use crate::graph::Hash;
 use crate::graph::Hashes;
-use anyhow::anyhow;
 use serde_derive::{Deserialize, Serialize};
 use std::collections::HashMap;
 use std::collections::HashSet;
@@ -56,10 +55,8 @@ pub struct Writer {
 
 impl Writer {
     fn new(ids: IdMap, w: fs::File) -> Self {
-        Writer {
-            ids,
-            w: BufWriter::with_capacity(IO_BUFFER_SIZE, w),
-        }
+        let w = BufWriter::with_capacity(IO_BUFFER_SIZE, w);
+        Writer { ids, w }
     }
 
     fn ensure_id(&mut self, graph: &Graph, file_id: FileId) -> anyhow::Result<Id> {
@@ -97,10 +94,15 @@ impl Writer {
     }
 }
 
-/// Reads an on-disk database, loading its state into the provided Graph/Hashes.
-fn read(mut f: fs::File, graph: &mut Graph, hashes: &mut Hashes) -> anyhow::Result<Writer> {
-    let mut rd = BufReader::with_capacity(IO_BUFFER_SIZE, &mut f);
-    let mut de = serde_cbor::Deserializer::from_reader(&mut rd).into_iter();
+/// Opens or creates an on-disk database, loading its state into the provided Graph.
+pub fn open(path: &str, graph: &mut Graph, hashes: &mut Hashes) -> anyhow::Result<Writer> {
+    let mut f = fs::OpenOptions::new()
+        .create(true)
+        .read(true)
+        .append(true)
+        .open(path)?;
+    let mut buf = BufReader::with_capacity(IO_BUFFER_SIZE, &mut f);
+    let mut de = serde_cbor::Deserializer::from_reader(&mut buf).into_iter();
 
     let mut ids = IdMap::new();
 
@@ -152,15 +154,3 @@ enum DbEntry {
         hash: Hash,
     },
 }
-
-/// Opens or creates an on-disk database, loading its state into the provided Graph.
-pub fn open(path: &str, graph: &mut Graph, hashes: &mut Hashes) -> anyhow::Result<Writer> {
-    match fs::OpenOptions::new().read(true).append(true).open(path) {
-        Ok(f) => read(f, graph, hashes),
-        Err(err) if err.kind() == std::io::ErrorKind::NotFound => {
-            let f = fs::File::create(path)?;
-            Ok(Writer::new(IdMap::new(), f))
-        }
-        Err(err) => Err(anyhow!(err)),
-    }
-}